The present invention relates to multi-sectioned fluid delivery devices with sensor membranes which can be used in the detection of target molecules in gas and liquid samples.
The detection of substances in various fluids by immunoassay methods is well known and used frequently for a variety of different purposes. Examples include the detection of antibodies in blood, urine, saliva or other biological fluids as an indication of the presence of a pathogen for diagnosis of various diseases and conditions. Other immunoassays of biological fluids include pregnancy tests and tests to determine blood alcohol level. More recently, immunoassays have been developed for detection of pollutants in environmental samples such as water and discharge from smoke stacks.
While such tests can be carried out as liquid assays, it is often easier and more convenient to spot the sample onto a solid substrate on which a ligand for the target molecule is immobilized and detect the presence of a specific binding complex. The most widespread immunoassay solid phase format used today is the enzyme-linked immunosorbent assay (ELISA).
An ELISA apparatus typically comprises a 96 well microtiter plate, the inside surfaces of which are coated with a ligand specific for a target molecule present in a sample. This binding or attachment of the ligand to the solid phase is not a chemical reaction but rather is believed to result from a physical or noncovalent interaction between the polystyrene matrix of the microtiter plate and the antigen. A sample suspected of containing the target molecule is placed in contact with the microtiter plate so that binding will occur between the ligand and any target molecule in the sample. Any unbound target molecules are then removed from the plate wells by several washing steps. A second ligand which specifically recognizes the target molecule and is linked to a signal-generating enzyme is then added. Detection of the enzyme which is indicative of the presence of the target molecule in the sample is typically performed by addition of reagents which produce a color change.
Performance of an ELISA can be quite time consuming. For example, an established method for screening for the AIDS virus is to first carry out an ELISA, followed by confirmation of positives by Western Blot. Generally, the ELISA takes about 4 hours and the Western Blot, which includes an overnight incubation period, requires about 20 hours. While this method may be adequate for routine screening of blood samples, it is not adequate for screening in organ transplant situations wherein results are required prior to the maximum ischemic time for the organ.
A similar technology, referred to as enzyme-linked immunofiltration assay (ELIFA), has been developed more recently in an attempt to overcome problems with false positive results and low sensitivity associated with ELISAs. ELIFAs function very similarly to ELISAs with the exception that ELIFA takes advantage of filtering the initial solution containing the ligand through a nitrocellulose membrane to bind it to the membrane. This filtering process facilitates xe2x80x9cimmunoconcentrationxe2x80x9d in that much higher levels of ligand bind to the membrane as compared to levels of ligand that bind to the surface of a microtiter plate. Target molecules in a sample are then bound to the ligand by incubation as in the ELISA method. However, any unbound target molecule is removed from the membrane by. filtration of the unbound molecules through the membrane into a waste chamber. Bound molecule is detected by precipitating a colored product on the membrane.
This type of porous solid substrate is, in theory, very useful since it permits removal of the bulk of the sample from the substrate while the target molecule remains at the surface bound to the immobilized ligand. However, in practice there are considerable difficulties due to slow flow of the sample through the substrate thus making this type of assay also very time consuming.
The present invention relates to a multi-sectioned fluid delivery device which is used in the ordered delivery of various fluids to a sensor membrane for detection of a targeted molecule bound to the sensor membrane.
A multi-compartment syringe is disclosed by Schreuder in U.S. Pat. No. 4,792,329. This syringe comprises an ampule having a plunger, a sealing stopper and at least one separating stopper between the plunger and the sealing stopper, and a needle holder consisting of a collar, a neck for an injection needle, a shaft between the collar and the neck and a by-pass means in the inner wall of the shaft, the space in the shaft of the needle holder being at least slightly longer that the sealing stopper, the ampule wall comprising a liquid by-pass means through which the liquid behind the separating stopper or stoppers can reach the substance in front of the separating stopper or front separating stopper and can mix with the same or can dissolve it, the ampule, before use of the syringe comprising an empty space in front of the sealing stopper. Thus, this device is different both functionally and in design from the multi-sectioned fluid delivery device of the present invention.
An object of the invention is to provide a multi-sectioned fluid delivery device which can be used for the ordered delivery of various fluids to a sensor membrane integrally linked or located within the multi-sectioned fluid delivery device. The delivery device of the present invention comprises a hollow syringe, and a piercing element and multiple individual compartments for separate storage of controlled amounts of various fluids located within the hollow syringe. Fluids are released from their individual compartments in the hollow syringe onto a sensor membrane in a prescribed sequence upon piercing of each compartment.
Another object of the present invention is to provide methods of using the multi-sectioned fluid delivery device in the detection of selected target molecules in a gas or liquid sample via a sensor membrane.